Climate and Average Weather Year Round in Kwajalein Atoll Marshall Islands

The climate in Kwajalein Atoll is hot, oppressive, windy, and overcast. Over the course of the year, the temperature typically varies from 79°F to 87°F and is rarely below 77°F or above 88°F.

Based on the beach/pool score, the best time of year to visit Kwajalein Atoll for hot-weather activities is from mid December to late April.

The temperature in Kwajalein Atoll varies so little throughout the year that it is not entirely meaningful to discuss hot and cold seasons.

In Kwajalein Atoll, the average percentage of the sky covered by clouds experiences mild seasonal variation over the course of the year.

The clearer part of the year in Kwajalein Atoll begins around December 10 and lasts for 7.2 months, ending around July 16.

The clearest month of the year in Kwajalein Atoll is March, during which on average the sky is clear, mostly clear, or partly cloudy 24% of the time.

The cloudier part of the year begins around July 16 and lasts for 4.8 months, ending around December 10.

The cloudiest month of the year in Kwajalein Atoll is November, during which on average the sky is overcast or mostly cloudy 85% of the time.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Kwajalein Atoll varies very significantly throughout the year.

The wetter season lasts 7.2 months, from May 3 to December 9, with a greater than 46% chance of a given day being a wet day. The month with the most wet days in Kwajalein Atoll is September, with an average of 20.5 days with at least 0.04 inches of precipitation.

The drier season lasts 4.8 months, from December 9 to May 3. The month with the fewest wet days in Kwajalein Atoll is February, with an average of 6.0 days with at least 0.04 inches of precipitation.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. The month with the most days of rain alone in Kwajalein Atoll is September, with an average of 20.5 days. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 74% on September 29.

Rainfall

To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Kwajalein Atoll experiences extreme seasonal variation in monthly rainfall.

Rain falls throughout the year in Kwajalein Atoll. The month with the most rain in Kwajalein Atoll is October, with an average rainfall of 8.0 inches.

The month with the least rain in Kwajalein Atoll is February, with an average rainfall of 1.8 inches.

The length of the day in Kwajalein Atoll does not vary substantially over the course of the year, staying within 39 minutes of 12 hours throughout. In 2024, the shortest day is December 21, with 11 hours, 35 minutes of daylight; the longest day is June 21, with 12 hours, 40 minutes of daylight.

The earliest sunrise is at 6:29 AM on May 27, and the latest sunrise is 42 minutes later at 7:12 AM on January 29. The earliest sunset is at 6:26 PM on November 15, and the latest sunset is 49 minutes later at 7:15 PM on July 14.

Daylight saving time (DST) is not observed in Kwajalein Atoll during 2024.

The figure below presents a compact representation of key lunar data for 2024. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases.

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The perceived humidity level in Kwajalein Atoll, as measured by the percentage of time in which the humidity comfort level is muggy, oppressive, or miserable, does not vary significantly over the course of the year, staying within 1% of 99% throughout.

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in Kwajalein Atoll experiences extreme seasonal variation over the course of the year.

The windier part of the year lasts for 7.1 months, from November 17 to June 22, with average wind speeds of more than 14.1 miles per hour. The windiest month of the year in Kwajalein Atoll is January, with an average hourly wind speed of 18.6 miles per hour.

The calmer time of year lasts for 4.9 months, from June 22 to November 17. The calmest month of the year in Kwajalein Atoll is September, with an average hourly wind speed of 9.7 miles per hour.

The predominant average hourly wind direction in Kwajalein Atoll is from the east throughout the year.

Kwajalein Atoll is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.

The average water temperature does not vary significantly over the course of the year, remaining within 1°F of 83°F throughout.

To characterize how pleasant the weather is in Kwajalein Atoll throughout the year, we compute two travel scores.

The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit Kwajalein Atoll for general outdoor tourist activities is from early January to mid March, with a peak score in the first week of February.

The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit Kwajalein Atoll for hot-weather activities is from mid December to late April, with a peak score in the last week of January.

Methodology

For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.

Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.

Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.

Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.

Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

Temperatures in Kwajalein Atoll are sufficiently warm year round that it is not entirely meaningful to discuss the growing season in these terms. We nevertheless include the chart below as an illustration of the distribution of temperatures experienced throughout the year.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy experiences some seasonal variation over the course of the year.

The brighter period of the year lasts for 2.8 months, from January 29 to April 22, with an average daily incident shortwave energy per square meter above 6.0 kWh. The brightest month of the year in Kwajalein Atoll is March, with an average of 6.5 kWh.

The darker period of the year lasts for 2.8 months, from August 28 to November 23, with an average daily incident shortwave energy per square meter below 4.6 kWh. The darkest month of the year in Kwajalein Atoll is October, with an average of 4.1 kWh.

For the purposes of this report, the geographical coordinates of Kwajalein Atoll are 9.182 deg latitude, 167.309 deg longitude, and 0 ft elevation.

The topography within 2 miles of Kwajalein Atoll is essentially flat, with a maximum elevation change of 0 feet and an average elevation above sea level of 0 feet. Within 10 miles is also essentially flat (0 feet). Within 50 miles is also essentially flat (0 feet).

The area within 2 miles of Kwajalein Atoll is covered by water (100%), within 10 miles by water (100%), and within 50 miles by water (100%).